View the musical or read the libretto several times. Make notes while taking in the show. What is strong in the performance? What is weak? What's missing? What might you like to focus on for your paper? Interpretations of a work of art can vary widely, but as long as they are justified and can be supported with evidence from the musical, they will be defensible.
Develop a paper topic. Pick a topic or question that you will address in your paper. Depending on the assigned essay length and any particular instructions you may have been given, craft a topic that will allow you to analyze one or more key elements of the performance. For instance: the quality of the players, the appropriateness of the set design, the structure of the acts or even the venue and its acoustics if you are watching a live performance. Alternatively, you can attempt to review how the musical hangs together, or how the players, the songs, the set, and so on work together to improve or hamper the quality of the musical.
Make an outline. Outline the key parts of your essay, including an introduction, several body paragraphs, and a conclusion. Make sure you have a thesis that ties each point together, and that each supporting point includes details. It is usually OK to use secondary sources for finding critiques and developing your own. If you are unsure, check with your instructor.
If placing arguments in your outline, highlight which are yours and which come from secondary sources.
Write and edit your paper. Write the paper, staying on topic, and edit it when finished. If possible, have a friend or colleague look over a draft. Read the paper aloud to yourself. This will help you catch any awkward or unclear passages. For a paper on a musical, you will want to quote from the piece if analysis the songs.